Ultimate mode

Ultimate mode is a special difficulty level accessed by typing ultimate on the title screen or running the game with the -ultimatemodecommand line parameter. When ultimate is typed on the title screen, the "Play without saving" save slot on the Select Game screen is automatically swapped with the "Ultimate mode" slot, which allows the game to be played in Ultimate mode. Typing ultimate again will undo this, restoring the slot to normal. Like the slot it replaces, the game will not be saved during the entire playthrough, so will have to be restarted from the beginning if the player dies. Ultimate mode differs from the normal game in these ways:

Beating specific levels, or clearing the whole game a specific amount of times, in Ultimate mode can be used as custom unlockable conditions. Beating the game in Ultimate mode does not give any rewards in regular SRB2 however.